last

last Function

Syntax:

last list &optional n → tail

Arguments and Values:

list—a list, which might be a dotted list but must not be a circular list.

n—a non-negative integer . The default is 1.

tail—an object.

Description:

last returns the last n conses (not the last n elements) of list). If list is (), last returns ().

If n is zero, the atom that terminates list is returned. If n is greater than or equal to the number of cons cells in list, the result is list.

Examples:

(last nil) → NIL 
(last ’(1 2 3)) → (3) 
(last ’(1 2 . 3)) → (2 . 3) 
(setq x (list ’a ’b ’c ’d)) → (A B C D) 
(last x) → (D) 
(rplacd (last x) (list ’e ’f)) x → (A B C D E F) 
(last x) → (F) 
(last ’(a b c)) → (C) 
(last ’(a b c) 0) → () 
(last ’(a b c) 1) → (C) 

(last ’(a b c) 2) → (B C) 
(last ’(a b c) 3) → (A B C) 
(last ’(a b c) 4) → (A B C) 
(last ’(a . b) 0) → B 
(last ’(a . b) 1) → (A . B) 
(last ’(a . b) 2) → (A . B) 

Exceptional Situations:

The consequences are undefined if list is a circular list. Should signal an error of type type-error if n is not a non-negative integer .

See Also:

butlast, nth

Notes:

The following code could be used to define last.

(defun last (list &optional (n 1))

(check-type n (integer 0))

(do ((l list (cdr l))

(r list)

(i 0 (+ i 1)))

((atom l) r)

(if (>= i n) (pop r))))

Expanded Reference: last

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